如何在 C# 4.0 中使任务进入睡眠状态（或延迟）？

Question

.NET 4.5 中有Task.Delay

如何在 .NET 4.0 中做同样的事情？

Answer 1

使用来自 NuGet 的 Microsoft.Bcl.Async 包，它有 TaskEx.Delay。

Answer 2

您可以在 4.0 中使用Timer 创建Delay 方法：

public static Task Delay(double milliseconds)
{
    var tcs = new TaskCompletionSource<bool>();
    System.Timers.Timer timer = new System.Timers.Timer();
    timer.Elapsed+=(obj, args) =>
    {
        tcs.TrySetResult(true);
    };
    timer.Interval = milliseconds;
    timer.AutoReset = false;
    timer.Start();
    return tcs.Task;
}

Answer 3

using System;
using System.Threading;
using System.Threading.Tasks;

class Program
{
    static void Main()
    {
        Delay(2000).ContinueWith(_ => Console.WriteLine("Done"));
        Console.Read();
    }

    static Task Delay(int milliseconds)
    {
        var tcs = new TaskCompletionSource<object>();
        new Timer(_ => tcs.SetResult(null)).Change(milliseconds, -1);
        return tcs.Task;
    }
}

来自How to implement Task.Delay in 4.0部分

Answer 4

以下是可取消的 Task.Delay 实现的代码和示例工具。您可能对Delay 方法感兴趣。：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DelayImplementation
{
    class Program
    {
        static void Main(string[] args)
        {
            System.Threading.CancellationTokenSource tcs = new System.Threading.CancellationTokenSource();

            int id = 1;
            Console.WriteLine(string.Format("Starting new delay task {0}. This one will be cancelled.", id));
            Task delayTask = Delay(8000, tcs.Token);
            HandleTask(delayTask, id);

            System.Threading.Thread.Sleep(2000);
            tcs.Cancel();

            id = 2;
            System.Threading.CancellationTokenSource tcs2 = new System.Threading.CancellationTokenSource();
            Console.WriteLine(string.Format("Starting delay task {0}. This one will NOT be cancelled.", id));
            var delayTask2 = Delay(4000, tcs2.Token);
            HandleTask(delayTask2, id);

            System.Console.ReadLine();
        }

        private static void HandleTask(Task delayTask, int id)
        {
            delayTask.ContinueWith(p => Console.WriteLine(string.Format("Task {0} was cancelled.", id)), TaskContinuationOptions.OnlyOnCanceled);
            delayTask.ContinueWith(p => Console.WriteLine(string.Format("Task {0} was completed.", id)), TaskContinuationOptions.OnlyOnRanToCompletion);
        }

        static Task Delay(int delayTime, System.Threading.CancellationToken token)
        {
            TaskCompletionSource<object> tcs = new TaskCompletionSource<object>();

            if (delayTime < 0) throw new ArgumentOutOfRangeException("Delay time cannot be under 0");

            System.Threading.Timer timer = null;
            timer = new System.Threading.Timer(p =>
            {
                timer.Dispose(); //stop the timer
                tcs.TrySetResult(null); //timer expired, attempt to move task to the completed state.
            }, null, delayTime, System.Threading.Timeout.Infinite);

            token.Register(() =>
                {
                    timer.Dispose(); //stop the timer
                    tcs.TrySetCanceled(); //attempt to mode task to canceled state
                });

            return tcs.Task;
        }
    }
}

Answer 5

从这个answer扩展这个想法：

new AutoResetEvent(false).WaitOne(1000);

Answer 6

您可以下载Visual Studio Async CTP 并使用TaskEx.Delay

Answer 7

在许多情况下，纯粹的 AutoResetEvent 比 Thread.Sleep()...

AutoResetEvent pause = new AutoResetEvent(false);
Task timeout = Task.Factory.StartNew(()=>{
pause.WaitOne(1000, true);
});

希望对你有帮助

Answer 8

    public static void DelayExecute(double delay, Action actionToExecute)
    {
        if (actionToExecute != null)
        {
            var timer = new DispatcherTimer
            {
                Interval = TimeSpan.FromMilliseconds(delay)
            };
            timer.Tick += (delegate
            {
                timer.Stop();
                actionToExecute();
            });
            timer.Start();
        }
    }

Answer 9

这是一个简洁的、基于计时器的实现，并进行了适当的清理：

var wait = new TaskCompletionSource<bool>();
using (new Timer(_ => wait.SetResult(false), null, delay, Timeout.Infinite))
    await wait.Task;

要在 .NET 4.0 上使用此代码，您需要 Microsoft.Bcl.Async NuGet 包。